Second level collation

My general goal is to have the least amount of different places where "todos" are managed. So my List is cluttered up with lots of stuff and tasks of very different kinds.
Example:
Jogging (private, not so important)
Creating a Document (work, very important, done over some time)
Appointments like flights (work, has to be done at a certain time)
Japanese Lessons (private, has to be done at a certain time)

I like to have a "general" overview. That means, I don't like to switch between different views (I use the Iphone Version a lot) but it seems that the View gets cluttered up with unimportant stuff (Jogging, Japanese lessons etc..) which makes it hard for me to prioritize.
So I use second level Sorting:
Due Date - Folder
That works for me pretty well but you can not see the second level very well in the Iphone and the website.
Thats why I think a second level collting (right word?) would be useful:
I imagine for example in the Iphone App that the first level sorting is like it is right now and the second level sorting paints the Background of the cells.
Maybe something similar is in the Website possible too?
This would allow to see in an instant: aha, this part is in the "private" Folder (less important) and this is in the "work" Folder
I am going wild here: Maybe a Button "switch first and second level sorting" would be very useful:
I see what I have to do today in private, work etc...
then press the "switch"-Button and scroll to the work Folder and see what I have to do work related today, tomorrow, the next week etc....
Also I think the "due time" Views are not ideal:
I can see "overdue" and "today" but cannot see "overdue and today" which is view that would IMHO be very useful. I never used the "due time".View because I have to switch constantly to get an overview